Hi Tapia1996. Welcome to the forum. To determine the cause of the failure, you have to autopsy the defective part. A very common cause of a new relay working where the old one didn't is rust buildup on the inner fender where it is mounted. There are actually two coils of wire inside the relay. Both of them get grounded through the metal mounting plate. Be sure the bolts are tight and free of rust. The next time this happens, have a test light ready and holler back before you disturb anything. Once you do anything that causes it to start working, there will be nothing to find and no defect to troubleshoot.
Sometimes the large copper nuts on the relay work loose and cause an intermittent no-crank. Replacing the relay will solve the problem since you tighten those nuts during the installation, but the real fix is to just tighten the nuts.
Another common problem is a corroded starter cable near where it bolts to the starter. The corrosion takes place under the insulation where you can't easily see it. The symptom is a single clunk from the relay when you turn the ignition switch to "crank", but the starter doesn't spin. Sometimes you will wiggle the cable enough when replacing the relay that the cable works again for a little while.
Friday, October 8th, 2010 AT 1:20 PM